NATE AC Service Certification Questions And Accurate Answers 2026/27

A system is supplied from the factory with charge of 5 pounds 10 ounces for a 15 foot line set. The line set is 25 feet long. The manufacturer's instruction sheet specifies 0.6 ounces of refrigeration to be added for each added foot of refrigerant line set length. What is the total refrigerant charge for the system? A. 6 ounces B. 5 pounds C. 5 pounds 10 ounces D. 6 pounds - CORRECT ANSWER D. 6 pounds 15ft - 25ft = 10ft x .6 = 6 ounces 5 pounds + 10 ounces + 6 ounces 5 pounds + 16 ounces = 6 pounds The purpose of using flux when soldering is to: A. anneal the surface. B. give better heat flow. C. reduce oxidation. D. pre-seal the oxidation. - CORRECT ANSWER C. reduce oxidation. Outdoor condensing units that are installed in areas where flooding is possible must: A. be mounted above flood level. B. utilize NEMA 1 enclosures. C. be mounted under an overhanging eave. D. use water resistant components. - CORRECT ANSWER A. be mounted above flood level. The component used to reduce sound transmission and prevent water leaks on a rooftop air conditioner packaged unit installation is the: A. curb gasket. B. silicone caulk. C. roof flashing. D. roofing tar. - CORRECT ANSWER A. curb gasket. Return air leakage in a hot attic will: A. Increase capacity B. Decrease capacity C. Increase airflow D. Decrease airflow - CORRECT ANSWER B. Decrease capacity An air conditioner refrigerant circuit should be evacuated to a minimum of: A. 0 microns. B. 200 microns. C. 500 microns. D. 1200 microns. - CORRECT ANSWER C. 500 microns. Which of the following substances could create an extremely dangerous condition if used to check refrigeration system for leaks? A. R-22 B. Nitrogen C. Oxygen D. Carbon Dioxide - CORRECT ANSWER D. Carbon Dioxide The subcooling method for checking charge is generally used on air conditioners with what type of metering? A. Only externally equalized thermostatic expansion valves B. Any thermostatic expansion valve C. Piston type D. Any fixed metering device - CORRECT ANSWER B. Any thermostatic expansion valve Supply ducts running through unconditioned space should be insulated and have: A. equal friction. B. excessive air velocity. C. a vapor barrier. D. a transition backing. - CORRECT ANSWER C. a vapor barrier. An important consideration when installing a motorized economizer is to check to be certain that: A. the vanes are set for a maximum 10% outdoor air. B. the vanes open on any call for cooling. C. the vanes operate without binding. D. the vanes are permanently set at 50%. - CORRECT ANSWER C. the vanes operate without binding. On a 3 ton unit installation, the measure airflow equals 1550 CFM. What does this indicate? A. Proper balancing B. Low Airflow C. Excess airflow D. Improper balancing - CORRECT ANSWER C. Excess airflow(400cfm per ton, 3 ton=1200cfm) Electronic type leak detectors typically have a push-button or knob for setting a reference refrigerant level. This feature is useful for: A. adjusting the detector after installing a new battery. B. checking the factory calibration of the instrument. C. setting the detector for use in environments with ambient refrigerant vapor. D. adjusting the detector for the type refrigerant to be checked. - CORRECT ANSWER C. setting the detector for use in environments with ambient refrigerant vapor. What will refrigerant oil in a hose cause when a technician is checking the pressures in an operation system with a manifold gauge set? A. All readings on that gauge will increase in value. B. All readings on that gauge will decrease in value. C. All readings on that gauge will not be affected. D. The gauge will read 0 psig. - CORRECT ANSWER C. All readings on that gauge will not be affected. Which measures duct static pressure? A. Anemometer B. Air balance hood C. Mechanical velometer D. Differential pressure gauge - CORRECT ANSWER C. Mechanical velometer A duct 36 in. x 24 in. that has an average velocity of 600 fpm is handling: A. 3600 CFM. B. 2400 CFM. C. 1200 CFM. D. 1000 CFM. - CORRECT ANSWER A. 3600 CFM. CFM = Velocity x Area (ft.^2) CFM = 600fpm x ((36 x 24)/144)) (convert to sq. ft.) CFM = 600fpm x 6sqft CFM = 3600 CFM What steps are necessary to clean a two row curved condenser coil? A. Spray the coil from the inside of the condenser with a soap base coil cleaner B. Spray the coil from the inside and the outside of the condenser with an acid base cleaner C. Brush the outside of the condenser with a bristle brush and water flush D. Separate the two rows of coils, spray all surfaces with proper coil cleaner and water flush - CORRECT ANSWER *D. Separate the two rows of coils, spray all surfaces with proper coil cleaner and water flush A residential supply diffuser that is noisy because of a loose vane is best serviced by: A. reducing the air volume. B. changing the fan speed. C. replacing the noisy vane. D. replacing the diffuser. - CORRECT ANSWER D. replacing the diffuser. Which of